This invention relates to novel rosin-fatty acid vinylic emulsion compositions and the process for preparing the same. In particular, the invention relates to novel rosin-fatty acid vinylic emulsion compositions which exhibit properties that make them useful as water-borne vehicles for coatings on various substrates.
Polymeric resins are commonly employed in a variety of different uses. For example, polymeric resins may be employed as support resins for ink formulations. Typical surfactant-based emulsion polymerization products generally do not have the rheology properties desired for graphic arts and coatings applications (i.e. film build, flow and leveling, and stability). It is, therefore, a common practice to add to the emulsion polymerization a low molecular weight water or alkaline soluble polymer (also referred to in the art as a resin) in place of, or in addition to, a surfactant in order to improve the stability and rheology properties of the emulsion.
Supported emulsions are commonly employed in paints, clear coatings, floor finishes, leather treatments, cement formulations, functional paper coatings, and graphic art applications. The latter encompasses pigmented (ink) and non-pigmented (overprints and functional coatings) formulations. A support emulsion is comprised of two polymers, one that represents the support resin and a second polymer that is dispersed into the support. The second polymer may be dispersed through agitation or actually be polymerized in the presence of the support resin. Supported emulsions add stability while enhancing the flow characteristics of the formulation (thereby resulting in higher gloss and clarity). Traditional polymer supports are commonly produced by the polymerization of acrylic acid or another vinylic acid and other vinyl monomers (see U.S. Pat. Nos. 4,839,413 and 5,216,064, which are hereby incorporated by reference). Other reactants and additives include initiators, solvents, and chain transfer agents. Upon completion of the reaction, any solvents employed may be removed yielding a support polymer. The support polymer then can be solubilized in a basic aqueous medium.
However, major problems exist with the traditional methods of producing polymer resins. For example, these methods require the use of environmentally adverse hydrocarbon solvents. Moreover, as these solvents are not usable or desirable in water-based ink or overprint formulations, the solvents must be stripped from the resulting acrylic polymers (thereby causing a yield loss). This stripping step also adds expense to the process due to both the losses of yield and the energy consumed in performing the stripping. Also, these methods must utilize chain transfer agents to regulate the molecular weight of the resulting support resin.
In the present invention, rosin-fatty acid vinylic polymers used as support resins for emulsion polymerization are produced preferably in bulk condition, thereby eliminating the costly stripping process for resin production. In addition, the resin polymerization can be performed at a higher temperature than traditional solution polymerization reactions. Moreover, as the present invention employs a lower amount of free radical initiator and little or no chain transfer agent, the resulting resins can be produced at a reduced cost (and unpleasant odors associated with chain transfer agents can be avoided).
Accordingly, one objective of this invention is to disclose a method of producing support resins comprised of rosin-fatty acid vinylic polymers and a method of producing emulsions using these rosin-fatty acid vinylic polymers as the support resins.
Although water-based inks are comprised of various components, the emulsion polymer (ink vehicle) is principally responsible for adhesion to the substrate. Adhesion is a quantitative description of the work of detachment between two phases under conditions of failure.
Polyolefin film substrates are difficult surfaces on which to achieve high adhesion due to their high surface energies and lack of functionality. Water-based inks in particular do not adhere well to film surfaces. Prior attempts to improve the adhesion of water-based inks include methods of increasing the polarity of the emulsion polymer vehicle through changes in monomer compositions including incorporation of vinyl chloride (see: Sisson et al., American Ink Maker, Vol. 78, pp. 44-47, August 2000 and U.S. Pat. No. 6,020,438). Amino-functional ink vehicles are also a way of obtaining adhesion to film substrates (U.S. Pat. No. 5,948,546). While these systems enhance adhesion, they have not found wide spread usage due to compatibility problems with the other ink components.
Therefore, an objective of this invention is to solve these problems by disclosing a rosin-fatty acid vinylic emulsion composition having improved adhesion to various substrates, including plastic, wood, metal, and flexible substrates like film and foil.
Alkyds generally are formed by the esterification polymerization of polyols and polybasic acid. The reaction mixture may also include monobasic acids, fatty acids and the like.
Due to their desired physical properties and low material costs, solvent-based alkyds have long been widely used as ingredients in coating compositions for various materials. For example, films resulting from aqueous alkyd coating compositions may be used as protective coatings for farm equipment and as a finish or refinish for trucks and automobiles. They are also extensively employed in architectural varnishes and enamels which require high gloss. However, rising health and environmentally concerns over the emission of organic compounds from solvent-based paints have resulted in strict regulation of the amount of volatile organic compounds (VOC) emitted from applied paints. In addition, rapid advances in technical innovation require improvements in the properties of coatings compositions. For example, it is desired that pigments be dispersed more effectively with higher stability in order to produce coating finishes having improved gloss (i.e., gloss at 60xc2x0) and distinctiveness-of-image gloss (i.e., gloss at 20xc2x0). Moreover, these coatings often exhibit problems with adhesion, flexibility, and resistance to corrosion and chemicals.
In an attempt to comply with the challenges of increased regulation and improved performance, industry has devoted much effort toward developing water-borne and high solid alkyds coatings which employ far lower amounts of organic solvents than conventional coatings. In spite of these substantial efforts, a need exists in the industry for such improved water-borne alkyds and high solid alkyds coatings.
High solid alkyds which employ less organic solvent than conventional alkyds often suffer from a dramatic increase in viscosity as the amount of solvent employed decreases. It has often been necessary for a high solid system to use lower molecular weight resins in order to maintain a workable paint viscosity. However, such systems tend not to develop the same hardness and through-dry in thick films in the same amount of time when compared to systems using higher molecular weight materials. Moreover, the additional functionality (which may build up the coating molecular weight after application) usually required for such high solid systems commonly results in adverse performance and higher production costs. One example of the use of additional functionality is to increase the level of unsaturated fatty acid to ensure sufficient crosslinking to achieve acceptable coating properties. One of the major drawbacks in the use of such high solid alkyds is the development of severe yellowing in the cured coatings due to the increased level of unsaturated fatty acid. U.S. Pat. No. 5,370,939 attempts to address this yellowing problem in alkyd coatings by teaching the incorporation of polyhydroxy based allyl ethers into alkyds to replace a part of or all of, the fatty acid. In U.S. Pat. No. 4,591,518, alkyd resins containing pendant polymerizable unsaturated groups attached to the alkyd through urethane linkages are claimed to improve high solid performance.
Water-borne alkyds coatings which use water as a dispersing medium are mainly emulsions and water-dispersible resins. Although showing an impressive success in replacing organic solvent coatings in many applications, water-borne alkyd coatings have not been able to satisfy the need of the coating industry in many applications because of certain inherent problems (e.g., insufficient gloss, water sensitivity, hydrolytic stability, and the difficulty of controlling water evaporation after application).
Coating compositions of acrylic polymers commonly provide finishes with excellent appearance, weatherability and durability. Coatings compositions of alkyds are known for their excellent gloss and their ability to be cured at ambient temperature. However, such alkyd coating compositions are also known for their inferior weatherability and durability when compared to acrylic finishes. Tremendous efforts have, therefore, been concentrated on developing interpolymers which are the combination of acrylic polymer and alkyd polymer.
Simply blending acrylic polymers and alkyds does not provide an optimum finish, as these acrylic polymer and alkyds are generally not compatible.
In the art of emulsions utilizing alkyd resins, interpolymer emulsions of acrylic polymers and alkyds have been prepared typically by following either one of two different procedures. In one procedure, an alkyd resin and compatible vinyl emulsion are separately formed, and then admixed together. By the other procedure, vinylic monomers are in situ polymerized in the presence of a preformed solution or dispersion of alkyd resin so as to provide an interpolymer system. The in-situ polymerization can take place with or without a conventional emulsifier. An example of this is U.S. Pat. No. 4,116,903, where a neutralized, aqueous solution of alkyd resin is utilized as sloe emulsifier to stabilize the in-situ vinylic emulsion polymerization.
In U.S. Pat. No. 4,273,690, an interpolymer is produced by grafting alkyd resin to the acrylic polymer backbone through urethane moiety. A number of patents have described the production of water-borne alkyds via the use polyurethane dispersion (see U.S. Pat. No. 3,412,054 and European Patent Application No. EP 0017199A1). Polyurethane dispersions or isocyanate compounds (which is the precursor for urethane moiety) are quite costly, and result in much higher production costs for water-borne alkyds when compared to conventional solventborne alkyds.
The water-borne alkyds often exhibit poor hydrolytic stability, in that they often do not have the capability to withstand storage for long periods of time at the high storage temperatures often found in warehousing and manufacturing facilities. Hydrolysis of alkyds may result in the separation of the coatings composition into phrases, accompanied by the settling of solid materials to the bottom or substantial reductions in viscosity and the diminished performance of the coating materials. U.S. Pat. No. 5,096,959, attempts to improve the hydrolytic stability of water-borne alkyds by reacting the base alkyd commonly used for such compositions with a polybasic acid composition comprising one or more cycloaliphatic polycarboxylic acids. However, this approach requires the use of costly cycloaliphatic polycarboxylic acids, thereby increasing production costs.
Therefore, another objective of this invention is to disclose rosin-fatty acid vinylic emulsion compositions that are useful as binders in paint, lacquers and coating compositions exhibiting water-borne alkyds performance with improved hydrolytic stability.
An attempt to improve the adhesion property of water-borne alkyds is disclosed in U.S. Pat. No. 4,649,175, which teaches the incorporation of nitrogen-containing compounds into the alkyds. This incorporation, however, increases the cost of production of such water-borne alkyds.
Another objective of this invention is to disclose a coatings composition comprising rosin-fatty acid vinylic emulsion compositions which exhibits excellent pigment dispersion and adhesion properties.
A further objective of this invention is to disclose a rosin-fatty acid vinylic emulsion compositions that providing a finish that could be cured at ambient and higher temperature with or without the crosslinkers and has an excellent appearance such as gloss (60xc2x0) and distinctiveness-of-image gloss (gloss at 20xc2x0), excellent physical properties like resistance to corrosion and chemicals, great elasticity and flexibility, and excellent adhesion to all types of coated and uncoated substrates.
In another aspect, the present invention provides rosin-fatty acid vinylic emulsion compositions which, when cured at ambient temperatures or when cured with or without a crosslinker under bake conditions, have gloss levels that are higher than those attainable with traditional vinylic polymer emulsions and gloss levels that are comparable or better than those of solventborne alkyds.
The emulsion compositions of the present invention can be formulated to pigmented or non-pigmented (clear) coatings. Such formulations exhibit the performance of water-borne alkyds, are easy to work with, and produce film coatings having excellent flow properties, high elasticity, outstanding weather resistance, good durability, superior gloss and color stability, exceptional chemical and water resistance, and less yellowing upon time. Wood varnishes produced from the compositions of the invention exhibit good penetration and good protective effects.
Another object of this invention is to disclose rosin-fatty acid vinylic emulsion compositions which exhibit ultra high initial gloss, excellent gloss and color stability, exceptional stain removal and stain resistance, and unique flexibility and elastomeric properties which allow them to be useful for formulating vehicles for water-based paints and other coating formulations.
A further object of this invention is to disclose rosin-fatty acid vinylic emulsion compositions which, when formulated into a water-based ink, impart flexibility to the ink.
Yet another object of this invention is to disclose rosin-fatty acid vinylic emulsion compositions which, when formulated into a water-based ink, improve the adhesion of the ink to film and foil substrates.
A further object of this invention is to disclose rosin-fatty acid vinylic emulsion compositions which, when formulated into a water-based overprint varnish, yield a high degree of gloss.
The objects of this invention are met via the production of rosin-fatty acid vinylic emulsion compositions using a method that employs rosin-fatty acid vinylic polymers as support resins for the emulsion polymerization reaction. These rosin-fatty acid vinylic emulsion compositions have enhanced properties (such as ultra high gloss, pigment dispersion, flexibility, adhesion, stain resistance, gloss and color stability, and elastomeric properties), which make the compositions highly desirable for a number of uses, including the formulation of overprint varnishes for coatings on paper and cellulose-based materials, the formulation of architectural and industrial paints for coating wood, plastic and metal substrates, and the formulation of ink vehicles for coating film and foil substrates.
Water-borne inks formulated with the rosin-fatty acid vinylic emulsion compositions exhibit excellent gloss, enhanced stability and increased adhesion to flexible substrates. Water-borne paints formulated with the rosin-fatty acid vinylic emulsion compositions exhibit excellent flexibility and gloss, an increased gloss and color stability over time.
The rosin-fatty acid vinylic emulsion compositions of the present invention are hybrid compositions containing a solventborne rosin-fatty acid component and a waterborne acrylic component on the same molecule. This unique combination gives the emulsion composition properties of both solventborne polymers and waterborne polymers. For example, the emulsion compositions have characteristics which permit the formulation of coatings exhibiting ultra-high gloss, excellent lay and hold-out properties, superior water and chemical resistances with sufficient crosslinking structures, compatibility with highly pigmented systems, exceptional grease resistance and resolubility. These characteristics allow the formulated coatings to function as good overprint varnish vehicles and ink vehicles on paper and cellulose-based materials. Additionally, the emulsion compositions further exhibit enhanced flow and leveling characteristics, package stabilities, exceptional stain resistance and stain removal, and excellent wet and dry adhesion to multiple substrates. These properties allow the emulsion compositions to function as superior binders in clear and pigmented paints for architectural, industrial, and maintenance coatings applications on metal, plastic, and wood substrates. When employed for coatings applications, the emulsion compositions allow an enhanced waterborne application having performances normally associated only with solventborne alkyd binders. Indeed, the emulsion compositions have proven to be superior to many solventborne alkyds in both gloss and color stability.
Due to increasing environmental concerns, industry has concentrated intensive efforts in the area of waterborne alkyds. However, the use of waterborne alkyds in the coatings market has heretofore been limited because of the higher production costs and lower gloss characteristics associated with traditional waterborne alkyds when compared to solventborne alkyds. Moreover, existing waterborne alkyds often suffer from hydrolytic instability (which can result in poor package stability and performance consistency). As the emulsion compositions of the present invention are hybrids of rosin-fatty acid acrylic technologies, the compositions exhibit acrylic characteristics of hydrolytic stability, color and gloss stability. At the same time, the emulsion compositions also exhibit polyester rosin-fatty acid character for flexibility and elasticity - which allow the emulsions to function as excellent waterborne ink vehicles and coatings binders for flexible substrates (i.e. plastic, film, foil, and the like).
To produce the emulsions of this invention, the vinylic monomers are copolymerized in an aqueous medium by adding the vinylic monomers to the rosin-fatty acid vinylic polymer solution, along with surfactants, if desired, and polymerizing catalysts or initiators. In certain cases, chain transfer agent could be employed to control molecular weight of the emulsion.
The rosin-fatty acid vinylic emulsion compositions of the present invention comprises the reaction products produced by:
(A) reacting in a first polymerization reaction:
(1) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(a) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of fatty acid, and
(b) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of rosin; and
(2) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(a) about 15.0% to about 45.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and combinations thereof,
(b) about 55.0% to about 85.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(c) about 0.5% to about 5.0% by total weight of the monomer mixture of a polymerization initiator,
(d) up to about 4.0% by total weight of the monomer mixture of a chain transfer agent, and
(e) up to about 30% by total weight of the monomer mixture of a hydrocarbon solvent,
at a temperature in the range of about 13 5xc2x0 C. to about 175xc2x0 C. to produce a rosin-fatty acid vinylic polymer having a weight average molecular weight in the range of about 4,000 to about 12,000; and
(B) further reacting in an emulsion polymerization reaction:
(1) about 5.0% to about 90.0% by total weight of the reactants of the rosin-fatty acid vinylic polymer of step A,
(2) about 10.0% to about 95.0% by total weight of the reactants of a member selected from the group consisting of vinylic monomers and combinations thereof, and
(3) about 0.5% to about 4.0% by total weight of the reactants of a polymerization initiator,
(4) up to about 4.0% by total weight of the reactants of a chain transfer agent, and
(5) up to about 4.0% by total weight of the reactants of a surfactant,
at a temperature in the range of about 20xc2x0 C. to about 100xc2x0 C. to produce a rosin-fatty acid vinylic emulsion composition having a weight average molecular weight in the range of about 40,000 to about 200,000.
Preferred rosin-fatty acid vinylic emulsion compositions comprise the reaction products produced by:
(A) reacting in a first polymerization reaction:
(1) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(a) about 20.0% to about 50.0% by total weight of the fatty acid rosin mixture of fatty acid, and
(b) about 50.0% to about 80.0% by total weight of the fatty acid rosin mixture of rosin; and
(2) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(a) about 20.0% to about 25.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and combinations thereof,
(b) about 60.0% to about 70.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(c) about 1.0% to about 3.0% by total weight of the monomer mixture of a polymerization initiator,
(d) about 0.5% to about 2.0% by total weight of the monomer mixture of a chain transfer agent, and
(e) about 1.0% to about 4.0% by total weight of the monomer mixture of a hydrocarbon solvent,
at a temperature in the range of about 140xc2x0 C. to about 1 70xc2x0 C. to produce a rosin-fatty acid vinylic polymer having a weight average molecular weight in the range of about 5,000 to about 11,000; and
(B) further reacting in an emulsion polymerization reaction:
(1) about 20.0% to about 60.0% by total weight of the reactants of the rosin-fatty acid vinylic polymer of step A,
(2) about 40.0% to about 80.0% by total weight of the reactants of a member selected from the group consisting of vinylic monomers and combinations thereof, and
(3) about 0.5% to about 1.5% by total weight of the reactants of a polymerization initiator,
(4) up to about 4.0% by total weight of the reactants of a chain transfer agent, and
(5) up to about 4.0% by total weight of the reactants of a surfactant,
at a temperature in the range of about 60xc2x0 C. to about 85xc2x0 C. to produce a rosin-fatty acid vinylic emulsion composition having a weight average molecular weight in the range of about 40,000 to about 180,000.
The first polymerization reaction used to produce the rosin-fatty acid vinylic polymer is a melt polymerization reaction in which no water is employed. Reaction temperatures suitable for use in the first polymerization reaction of the present invention are within the range of about 135xc2x0 C. to about 175xc2x0 C.; with the preferred temperatures being in the range of about 140xc2x0 C. to about 170xc2x0 C. These rosin-fatty acid vinylic polymers have characteristics that differ from the traditional melt blends of flake acrylic fatty acid rosin. For example, the low molecular weights of the rosin-fatty acid vinylic polymers enable the polymers to be neutralized at high solid levels while maintaining low viscosities. The low molecular weight coupled with the polymer""s high levels of functional carboxyl units permits the production of rosin-fatty acid vinylic emulsion compositions that are well-suited for use in water-based inks, paints, and other coating applications as these emulsions tend to improve both the gloss and the leveling properties of formulated inks as well as the stability of formulated paints.
In the first polymerization reaction, the rosin and fatty acid function as solvents in the polymerization of the acrylic monomers. Additionally, while a portion of the fatty acid and the rosin component remains unreacted, some of the fatty acid and rosin becomes graft polymerized onto the acrylic. It is preferred to employ a bulk polymerization process for the first polymerization reaction. The residence time for such bulk processes is commonly in the range of about 3 hours to about 10 hours. However, where desired the first polymerization reaction may be conducted via the use of a continuous stirred polymerization process. The residence time for such continuous processes is commonly in the range of about 90 minutes to about 6 hours; with the preferred residence time being in the range of about 2 hours to about 3 hours.
The rosin-fatty acid vinylic polymers of the first polymerization reaction have a weight average molecular weight in the range of about 4,000 to about 12,000; with the preferred molecular weight being in the range of about 5,000 to about 11,000.
Rosin-fatty acid vinylic polymers which are suitable for use as a support resin for the emulsion polymerization reaction have an acid number commonly in the range of about 175 to about 500; with the preferred range being about 190 to about 230. However, the acid number range will vary depending upon the respective application of the rosin-fatty acid vinylic emulsion compositions. For example, when aqueous dispersions of the rosin-fatty acid vinylic compositions are employed as surface sizing compositions for cellulosic materials, a suitable acid number is in the range of about 50 to about 500; with the preferred range being about 50 to about 250. It is well within the ability of one skilled in the art to determine proper acid number ranges for various applications.
Fatty acids which are suitable for use in the present invention include those fatty acids which contain a range of carbon atoms from about C12 to about C24, with the preferred range being from about C16 to C20. It is further preferred that the fatty acid be vegetable or tall oil based. It is most preferred that the fatty acid be tall oil based and contain from about 15% to about 18% conjugated double bonds.
While from about 10% to about 90% by total weight of the fatty acid rosin mixture may be fatty acid, a preferred range of fatty acid is from about 20% to about 50% by total weight of the mixture.
Rosins which are suitable for use in the present invention include wood rosin, tall oil rosin, gum rosin, and the like. The use of tall oil rosin is preferred. While from about 10% to about 90% by total weight of the fatty acid rosin mixture may be rosin, a preferred range of rosin is from about 50% to about 80% by total weight of the mixture.
While from about 15% to about 45% by total weight of the monomer mixture employed in the first polymerization reaction may be a member selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and combinations thereof; a preferred range is from about 20% to about 25% by total weight of the mixture.
While from about 55% to about 85% by total weight of the monomer mixture may be a member selected from the group consisting of vinylic monomers and combinations thereof; a preferred range is from about 60% to about 70% by total weight of mixture.
Vinylic monomers which are suitable for use in both the first polymerization reaction and the emulsion polymerization reaction in the present invention include styrenic monomers, acrylic monomers, methacrylic monomers, ethylenic monomers, and the like. In the first polymerization reaction, it is preferred that the vinylic monomers be a mixture, preferably including at least one monoalkenyl aromatic monomer and at least one acrylic monomer. The monoalkenyl aromatic monomer to be employed includes, for example, alpha-methyl styrene, styrene, vinyl toluene, tertiary butyl styrene, ortho-chlorostyrene and mixtures thereof.
The term xe2x80x9cacrylic monomerxe2x80x9d as employed herein includes members of the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, derivatives of acrylic acid, derivatives of methacrylic acid, and combinations thereof. Examples of suitable acrylic and methacrylic ester monomers include the C1-C30 alkyl ester derivatives. Methacrylic esters suitable for use in the present invention include, but are not limited to, the following: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, isoamyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, 2-sulfoethyl methacrylate, trifluoroethyl methacrylate, glycidyl methacrylate, benzyl methacrylate, allyl methacrylate, 2-n-butoxyethyl methacrylate, 2-chloroethyl methacrylate, sec-butyl-methacrylate, tert-butyl methacrylate, 2-ethybutyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, furfuryl methacrylate, hexafluoroisopropyl methacrylate, methallyl methacrylate, 3-methoxybutyl methacrylate, 2-methoxybutyl methacrylate, 2-nitro-2 methylpropyl methacrylate, n-octylmethacrylate, 2-ethylhexyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate, phenyl methacrylate, propargyl methacrylate, tetrahydrofurfuryl methacrylate and tetrahydropyranyl methacrylate.
Typical acrylate esters suitable for use in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-decyl acrylate, 2-ethylhexal acrylate, and the like.
Typical methacrylic acid derivative acrylic monomers suitable for use in the present invention include methacrylic acid derivatives such as: methacrylic acid and its salts, methacrylonitrile, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N,N-diethymethacrylamide, N,N-dimethylmethacrylamide, N-phenyl-methacrylamide, methacrolein, and the like.
Acrylic acid derivatives suitable for use as the acrylic monomer include: acrylic acid and its salts, acrylonitrile, acrylamide, methyl alpha-chloroacrylate, methyl 2-cyanoacrylate, N-ethylacrylamide, N,N-diethylacrylamide acrolein, and the like.
Typical ethylenic monomers suitable for use in the present invention include vinyl acetate, derivatives of vinyl acetate, vinyl chloride, derivatives of vinyl chloride, vinyl pyridine, vinyl pyrollidone, sodium crotonate, methyl crotonate, crotonic acid, maleic anhydride, and the like.
For the first polymerization reaction, from about 0.5% to about 5.0% by total weight of the monomer mixture is a polymerization initiator, with a preferred range being from about 1.0% to about 3.0% by total weight of the mixture. Polymerization initiators which are suitable for use in the first polymerization reaction include, but are not limited to, the following: t-butyl peroxide, t-butyl peroxybenzoate, t-butyl peroctoate, cumene hydroperoxide, azobisisobutyronitrile, benzoyl peroxide, and combinations thereof.
For the emulsion polymerization reaction, from about 0.5% to about 4.0% by total weight of the reactants is a polymerization initiator, with a preferred range being from about 0.5% to about 1.5% by total weight of the reactant mixture. The type of polymerization initiator suitable is known in the art to depend upon the desired temperature for the reaction. Suitable initiators include thermal initiators, redox initiators, and combinations thereof. Thermal initiators which are suitable for use include, but are not limited to, the following: hydrogen peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, benzoyl peroxide, benzoyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, t-butyl peracetate, azobisisobutyronitrile, ammonium persulfate, sodium persulfate, potassium persulfate, isopropyl peroxycarbonate, and combinations thereof. Suitable redox initiators include, but are not limited the following: sodium persulfate-sodium formaldehyde sulfoxylate, cumene hydroperoxide-sodium metabisulfite, potassium persulfate-sodium metabisulfite, potassium persulfate-sodium bisulfite, cumene hydroperoxide-iron (II) sulfate, and combinations thereof.
Where desired, a chain transfer agent may be employed in both polymerization reactions. Chain transfer agents which are suitable for use in the present invention include, but are not limited to, the following: dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid, octyl mercaptan, 2-mercaptoethanol, and combinations thereof. While up to about 4.0% by total weight of the monomer mixture may be a chain transfer agent; where employed it is preferred to use an amount in the range of from about 0.5% to about 2.0% by total weight of the mixture.
Where desired, a hydrocarbon solvent may be employed in the first polymerization reaction. Suitable hydrocarbon solvents include aromatic solvents, aliphatic solvents, and combinations thereof. While up to about 30.0% by total weight of the monomer mixture may be a hydrocarbon solvent; where employed it is preferred to use an amount in the range of about 1.0% to about 4.0% by total weight of the mixture.
An emulsion polymerization reaction is employed to produce the rosin-fatty acid vinylic emulsion compositions. Reaction temperatures suitable for use in the emulsion polymerization reaction of the present invention are within the range of about 20xc2x0 C. to about 100xc2x0 C.; with the preferred temperatures being in the range of about 60xc2x0 C. to about 85xc2x0 C. The resulting rosin-fatty acid vinylic emulsion compositions have a weight average molecular weight in the range of about 40,000 to about 200,000; with the preferred molecular weights being in the range of about 40,000 to about 180,000.
Where desired, a surfactant may be employed in the emulsion polymerization reaction in an amount up to about 4.0% by weight of the reactants. Surfactants which are suitable for use in the present invention include members selected from the group consisting of anionic surfactants, non-ionic surfactants, and combinations thereof. Suitable anionic surfactants include alkyl sulfates, ether sulfates, phosphate esters, sulfonates, and the like. Suitable non-ionic surfactants include alcohol ethoxylates, alkylphenol ethoxylate, phenol ethoxylate, block copolymers, and the like. Anionic and non-ionic surfactants containing polymerizable groups (known in the art as xe2x80x9cpolymerizable surfactantsxe2x80x9d) are also suitable for use in the present invention.
It is well within the ability of one skilled in the art to produce an aqueous base suitable for use in dissolving the rosin-fatty acid vinylic emulsion compositions. Such aqueous bases include those produced using organic solvents and various inorganic solvents (such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, amines, sulfates, and the like).
As appreciated in the art, the exact components and properties of components desired for any coating application can vary and, therefore, routine experimentation may be required to determine the optional components and proportions of components for a given application and desired properties.
The following examples are provided to further illustrate the present invention and are not to be construed as limiting the invention in any manner.